Somatosensory Pathway

Question 1

Two
major “long tracts” of the nervous system; these are the somatosensory
pathways:

Answer 1

posterior column–medial lemniscal system and the

anterolateral systems

Question 2

The term somatosensory generally refers to

Answer 2

bodily sensations of touch, pain, temperature,

vibration, and proprioception (limb or joint position sense).

Question 3

posterior column–medial lemniscal pathway conveys

Answer 3

proprioception,

vibration sense, and fine, discriminative touch

Question 4

anterolateral pathways include the spinothalamic tract and other associated
tracts that convey

Answer 4

pain, temperature sense, and crude touch

Question 5

Since some aspects of touch sensation are carried by both pathways, touch sensation
is not eliminated in

Answer 5

isolated lesions to either pathway.

Question 6

Larger-diameter, myelinated

axons conduct faster than

Answer 6

smaller-diameter or unmyelinated axons.

Question 7

Sensory neuron cell bodies are located in the

Answer 7

dorsal root ganglia

Question 8

Each dorsal root ganglion cell has a stem axon that bifurcates, resulting
in one long process that conveys sensory information from the periphery
and a second process that carries information
into

Answer 8

the spinal cord through the dorsal nerve roots.

Question 9

A peripheral region innervated by sensory fibers

from a single nerve root level is called a

Answer 9

dermatome.

Question 10

The dermatomes for the different spinal levels form

a map over the surface of the body that can be useful in localizing

Answer 10

lesions of the nerve

roots or spinal cord.

Question 11

corticospinal tract

crosses over at

Answer 11

the pyramidal decussation helps us

localize CNS lesions

Question 12

PATHWAY: Lateral corticospinal tract

FUNCTION:

NAME (AND LEVEL) OF DECUSSATION:

Answer 12

PATHWAY: lateral corticospinal tract

FUNCTION: Motor

NAME (AND LEVEL) OF DECUSSATION: Pyramidal decussation (cervico-medullary junction)

Question 13

PATHWAY: Posterior column-medial lemniscal pathway

FUNCTION:

NAME (AND LEVEL) OF DECUSSATION:

Answer 13

PATHWAY: Posterior column-medial lemniscal pathway

FUNCTION: Sensory (vibration, joint position, fine touch)

NAME (AND LEVEL) OF DECUSSATION: Internal arcuate fibers (lower medulla)

Question 14

PATHWAY: Anterolateral pathways

FUNCTION:

NAME (AND LEVEL) OF DECUSSATION:

Answer 14

PATHWAY: Anterolateral pathways

FUNCTION: Sensory (pain, temperature, crude touch)

NAME (AND LEVEL) OF DECUSSATION: Anterior commissure (spinal cord)

Question 15

NAME: A-alpha
ALTERNATE NAME:
FIBER DIAMETER (μm):
MYELINATED:
RECEPTORS:
SENSORY MODALITIES:

Answer 15

NAME: A-alpha
ALTERNATE NAME: I
FIBER DIAMETER (μm): 13 - 20
MYELINATED: Yes
RECEPTORS: Muscle spindle; Golgi tendon organ
SENSORY MODALITIES: Proprioception; Proprioception

Question 16

NAME: A-beta
ALTERNATE NAME:
FIBER DIAMETER (μm):
MYELINATED:
RECEPTORS:
SENSORY MODALITIES:

Answer 16

NAME: A-beta
ALTERNATE NAME: II
FIBER DIAMETER (μm): 6 - 12
MYELINATED: Yes

RECEPTORS [SENSORY MODALITIES]:

Muscle
spindle [Proprioception]

Meissner’s
corpuscle [Superficial touch]

Merkel’s
receptor [Superficial touch]

Pacinian corpuscle [Deep touch, vibration]

Ruffini ending [Deep touch, vibration]

Hair receptor [Touch, vibration]

Question 17

NAME: A-delta
ALTERNATE NAME:
FIBER DIAMETER (μm):
MYELINATED:
RECEPTORS:
SENSORY MODALITIES:

Answer 17

NAME: A-delta
ALTERNATE NAME: III
FIBER DIAMETER (μm): 1 - 5
MYELINATED: Yes
RECEPTORS [SENSORY MODALITIES]:

Bare nerve ending [Pain]
Bare nerve ending [Temperature (cool)]
Bare nerve ending [Itch]

Question 18

NAME: C
ALTERNATE NAME:
FIBER DIAMETER (μm):
MYELINATED:
RECEPTORS:
SENSORY MODALITIES:

Answer 18

NAME: C
ALTERNATE NAME: IV
FIBER DIAMETER (μm): 0.2 - 1.5
MYELINATED: No
RECEPTORS [SENSORY MODALITIES]: 

Bare nerve ending [Pain]
Bare nerve ending [Temperature (warm)]
Bare nerve ending [Itch]